Failure of an antagonist of histamine--chlorpheniramine--to modify the pulmonary vascular response to hypoxia in chronic bronchitis.

Experimental evidence from animals suggests that the response of the pulmonary circulation to hypoxia is mediated by histamine. In 3 patients with chronic bronchitis the pulmonary vascular response to hypoxia was measured before and after administration of chlorpheniramine, a competitive antagonist of histamine. No convincing evidence was obtained of a reduction in the size of the response to hypoxia.